1. It does. But very slowly, because the current density on it is X50 smaller than that on the WE. Therefore, it is negligible.

2. See above :)

3. No.

I second that.. it is good practice to use a 50X larger CE, even better would be using an inert one with a higher exchange current density.

If I have understood correctly, your experiment was run using WE & CE of same material and SCE using electrolyte. In the beginning of the experiment before connection, the electrodes were immersed and kept for stabilization of open circuit corrosion potential. and then you made connections and applied anodic Tafel current to WE.

Ans 1) Now, one thing to note here is, as soon as you apply anodic Tafel current to the WE through potentiostat, CE automatically becomes more "cathode". It has to become a cathode in principles (Faraday laws). So it will never corrode while anodic polarization of WE.

The confusion starts with the figures because of negative sign. -1010 mV is not a corrosion potential for CE but actually cathodically protecting CE.

Ans 2) The CE is generally the material that should not corrode in given electrolyte. The noble materials are chosen as counter electrodes. Its not important to consider CE potential except it is getting corroded during experiment unfortunetly.

I hope this helps. I could not understand 3rd question I think.

1. See Pourbaix diagrams. You enter in the immunity domain. In reality you do not stop corrosion but is lower than 0.001 mm/year. This is the principle of cathodic protection.

2. The soft take into account this potential.

3. No. Ecorr is obtained as intersection of tangent at anodic and cathoic polarisation curves

Inspite of the high exposed surface area ratio, corrosion is not expected at the cathode. When you applied polarization on the system you were in effect cathodically protecting your cathode while sacrificing your anode. This is the principle of cathodic protection of corrosion prone assets.

Change the polarities and see that the reverse becomes the case.. The potential of the CE is not critical as it functions to complete the circuit ( hence inert materials like platinum are favoured.

Suppose your solution was acidic with low pH, Fe is oxidized to Fe2+ and enter the solution (corrosion) while mainly hydrogen evolution occurs at your cathode.

Agreed with Stanley and Ishan. Cathodes are protected by anode by sacrificial process. Anodic counter electrodes are made with Pt mesh for their low corrosion. But when counter electrodes are cathodes, corrosion may not be issue. This process will however involve deposition of cations on counter electrode (cathode).

1) Normally, I do not choose the same material for WE and CE. In the system you described, there is a cathodic protection on the steel CE. Althought the cathodic potential is much negative than the anodic potential, it does not reflect the susceptiblity of the CE.

2) We care about CE. In the case of your system, the CE will be damaged as well because the very large amount of hydrogen produced owing to hydrogen evolution reaction. The hydrogen will migrate in the steel very easily, resulting in mechanical and chemical change, for example, hydrogen embrittlement. From my understanding, noble metal, such as Pt, Au and Pd, are not considered to be susceptible to hydrogen embrittlement.

3) It is not Ecorr.

I agree with Stanley Ofoegbu · University of Aveiro

You have large area of CE, so the cathodic protection occurs, also, as usual the CE electrode is always inert material e.g Pt because its function is complete the circuit in cell

To: Alex Lugovskoy, Jan Vaes, Ishan Patel, Razvan George Ripeanu, Stanley Ofoegbu, Parijat Bhatnagar, Luning Wang & Amin El-Meligi.

Thanks for all your time & your answers. I really appreciate it. Now I understand what is CE. Thanks again.

You're using your potentiostat to anodically "polarize" your Working Electrode, or drive it to a more positive potential. The Reference and Counter Electrodes are only there because your three-electrode potentiostat needs them to control the potential difference between the Working and Reference Electrodes. As long as the potentiostat is accurately controlling the potential and measuring the current at the Working Electrode, you don't care what is happening at the Counter Electrode. But if you decide that you do care about the potential of the Counter Electrode, but careful when measuring it. It's not particularly easy and you should consult your potentiostat supplier for their recommended procedure. Regarding your questions: (1) The Counter Electrode does not corrode/oxidize because the potential of the Counter Electrode is negative of the Eoc, so only a reduction can occur on the Counter. (2) In general, users of potentiostats only care about the potential and current of the Working Electrode. If there are no overload conditions or loss of potentiostatic control, then the Reference and Counter Electrodes are doing their job properly. (3) The Eo (or Eoc or Ecorr) is the potential at which the measured current is zero and is the result of a "mixed potential".

Many thanks Mr Peterson. Your explanation make me so confident to my experiments. Thanks again.

I agree with Mr. Peterson. I do have suggestion for your anodic polarization test. Most research concern about W.E, since W.E is the test sample from my understanding. If you doing Tafel or polarization from cathodic potential or anodic potential, you need to determine your actual sample. Since your are using same material for W.E and C.E, you need to consider the possibly of W.E(steel) that might be affected by the test solutions. Im suggesting that you use much noble, non corroded C.E such as platinum so that the measurement on W.E will not be affected. You can adjust the surface area of the W.E since the surface you will be using for your data is the W.E surface. Also E.O is also known as Open circuit potential or natural potential where the charge transfer is most likely in equilibrium where this potential that corrosion will start to occur. If I wrong please forgive me.

Assalamualaikum,

Muhammad Zaimi , thanks you very much. I appreciate your answer. It is quite difficult to find partners in the field of corrosion in Malaysia. You will be my corrosion friends.

I should have been a bit more specific and said...(3) The Eo (or Eoc or Ecorr) of the Working Electrode is the potential at which the measured current at the Working Electrode is zero and is the result of a "mixed potential".

Waalaikumussalam warahmatullah. You can always contact me by email Mr. Shaiful.